Document: ALE-3-42-21

Nitrogen supply effects on compensatory growth and reproduction in response to herbivore damage: A test of the RGR trajectory hypothesis with Abutilon theophrasti.

WAIT, D.A.*

Southwest Missouri State University, Springfield, MO 65804, U.S.A. ¹

Abstract:
I tested the hypothesis that the trajectory of a plants relative growth rate (RGR) determines compensatory growth and reproduction to herbivore damage. A positive trajectory is when the slope of RGR is greater than zero, a constant trajectory is when the slope of RGR is zero, and a negative trajectory is when the slope of RGR is less than zero. Abutilon theophrasti was grown at two nitrogen concentrations and three nitrogen (N) supply rates in a greenhouse as follows: no added nitrogen, one addition of N when the plants had two true leaves, additions of N every four days until flowering. I clipped 75% of the area off all leaves, clipped 75% of the area of each leaf as it reached 50% of full expansion, removed 75% of the leaves, or damaged 75% of the area of all leaves using a file. RGR trajectories and compensatory growth and reproduction were determined or estimated by frequent harvests of plants, and frequent measures of plant height and leaf area. Compensatory growth and reproduction were greatest in plants with a constant as opposed to a positive or negative RGR trajectory independent of damage regime and N supply treatment. These experiments indicate that RGR trajectory, which is a measure of a plants N supply:demand ratio, and not high or low N availability per se, can be used to predict growth and reproduction responses following herbivory.

Keywords: Herbivore damage, compensatory growth and reproduction, nitrogen supply:demand; RGR trajectory; exponential nitrogen supply

This abstract is being presented at: 3:30 PM in session:
HERBIVORE EFFECTS ON PLANTS